It should ask for those documents in the document checklist at the end of the application form.
They do need to be included though - in the past, when they have not been included, UKVI has had to contact the applicants to request the required documents be sent to them… which can slow down the processing time.
The reason those documents need to be included for children is that if the visa falls for refusal and they look at whether you qualify to be put onto the 10-year path to ILR instead of leaving the UK, they will usually only allow it if you have a UK citizen child living in the UK whose life would be severely impacted if you had to return to your home country.
I can’t see the online form myself without completing an application, but here is some of the document guidance from the old SET(M) paper form (2018). The document requirements have not changed since then:
Link to the paper form:
http://bingham.butterworths.co.uk/PDF/level1/hosetm.pdfSent from my iPhone using Tapatalk